Performance between SI and VTEC

[Alan999]

Hello prelude enthusiasts…

I was wondering how the gas mileage was for people who have swaped their 2.3l for a VTEC engine. In a regular commute (not racing) do you all feel that the mileage that you are getting is better from a 2.2 VTEC engine than a 2.3l engine. Or would you say there is no difference…. Any opinion is appreciated….

Also is it true that the VTEC engine burns (or consumes) oil….that u have to keep a watch on the oil level constantly.

Thanks for your in put in advance…..cheers

[Gohan Ryu]

I own a 92 si and a 96 vtec and the 96 gets slightly better gas mileage. If I drive the 96 with a heavy foot (always in vtec) then the mileage suffers, but I always get better mileage with the 96. BTW my 96 is in better shape my 92, so that might have something to do with it. Both engines are mostly stock.

[94PreludeJDM]

Yeah it is true that the VTEC engines use oil, mostly due to the high RPM's. Mine really doesn't use any oil, i had a slow leak that I had fixed and the most i'll have to put in is half a quart in between oil changes, if that. But especially when the miles start to get higher, they do have a tendancy to burn oil.

[SiGNAL748]

Originally Posted by Gohan Ryu

I own a 92 si and a 96 vtec and the 96 gets slightly better gas mileage. If I drive the 96 with a heavy foot (always in vtec) then the mileage suffers, but I always get better mileage with the 96. BTW my 96 is in better shape my 92, so that might have something to do with it. Both engines are mostly stock.

I also own a 96 VTEC. This might be a long shot but I think the fact that they're OBDII has something to do with them having slightly better gas mileage. OBDII cars will tend to run within certain a/f parameters to keep them emissions friendly. While if an OBDI car tends to run rich, it will continue to run rich without much correction from the ecu, thus using a bit more fuel.

[Gohan Ryu]

Originally Posted by SiGNAL748

I also own a 96 VTEC. This might be a long shot but I think the fact that they're OBDII has something to do with them having slightly better gas mileage. OBDII cars will tend to run within certain a/f parameters to keep them emissions friendly. While if an OBDI car tends to run rich, it will continue to run rich without much correction from the ecu, thus using a bit more fuel.

Yup, I agree - my 92 always has that black carbon burnt-fuel residue on the tailpipes from running too rich - keeps coming back after I clean it off. The 96 tailpipes stay pretty clean.

[94PreludeJDM]

I never even thought of that. My 94 has the burnt fuel residue on the tailpipes too. I know that they're known for running rich at higher RPM's too. You think a dyno tune with a VAFC to lean it out a little would increase gas mileage?

[SiGNAL748]

Originally Posted by 94PreludeJDM

I never even thought of that. My 94 has the burnt fuel residue on the tailpipes too. I know that they're known for running rich at higher RPM's too. You think a dyno tune with a VAFC to lean it out a little would increase gas mileage?

Well, Honda motors, especially VTEC's, will tend to run rich by default. Honda tuned them that way as somewhat of a safety precaution (to prevent detonation). I suppose that if the person tuning your car knew what he was doing, it shouldn't be too much of a problem.

[94PreludeJDM]

Yeah I knew it was to prevent detonation. I think it might have been AcesHigh who posted it some time ago, but he had the A/F ratios at different RPM's, and apparently there's a decent amount of power that can be freed up. Like you said though, as long as the person knows what they are doing.

[SiGNAL748]

Where's Aces been lately anyway? He had some pretty good faqs going a while back.

[Alan999]

Thanks guys for your input...

How about others with vtec do your engines burn oil as well with you vtec motors. Is it a problem that occurs when you run at high rpm or does the vtec burn oil as part of its normal operation. Also does this problem occur on the 2.3l engine as well..

Thanks guys i'm just trying to make up my mind between a si and vtec,
Alan.

[94PreludeJDM]

Yeah Signal, I was wondering the same thing, he seems to come and go, but he knows his stuff.

To Alan999, if you can get the vtec, it's no question, get the vtec, it's so much fun to drive. As long as the engine is taken care of, the amount of oil consumed is next to nothing. It shouldn't consume more than 1 quart between oil changes. Unless you plan on boosting, go with the vtec.

[AcesHigh]

Hello everyone, apologies for the recent absence.

Anyways VTEC doesn't burn any more oil than a standard engine, although it is true that oil is an especially important component. Much like a turbocharger, without oil running there would be no VTEC operation. It uses a little extra oil, but it won't necessarily burn it.

Use of a fuel computer such as a VAFC to run the system ever so slightly lean at higher RPMs would unlock a bit more power, and would be ideal in climates where temperatures wouldn't get too cold (although you could always reset the VAFC to default in cooler weather). There's always a fear of burning something inside, which is why Honda set the fuel a little rich (that fear is accentuated in the higher revolutions).

[Janet Reno]

From what I know unless you actually get into VTEC the oil use is the same. I've heard of people who run in the twisties in the hills and are in VTEC for several minutes notice that it uses more oil than regular.

[honda_racing101]

YAY! aces if finally back...been wonder where you were...Prelude forums have been kinda dead while you were gone

[Prelewd]

Anytime you run your engine in the higher RPMs, oil consumption is going to be higher..